Spacer element for a collect chuck and collect chuck

ABSTRACT

Collet chucks ( 20 ) comprise at least two tensioning segments ( 21 ). Adjacent tensioning segments are connected to each other by means of elastic spacer elements ( 30 ). The tensioning segments ( 21 ) have back-cuts ( 22 ), whilst the spacer elements have correspondingly formed sections ( 36 ). A positive fit of the formed sections in the back-cuts of the tensioning segments ( 21 ) is thus possible.

FIELD OF APPLICATION AND PRIOR ART

[0001] The present invention relates to a spacer element for a colletchuck according to the preamble of claim 1 and to a collet chuck, suchas is in particular used for chucking workpieces.

[0002] Collet chucks comprise several cooperating gripping or clampingsegments, which are displaceable relative to one another in order toe.g. firmly hold workpieces of different size, force and/or shape.

[0003] Such connections between clamping segments are e.g. brought aboutby corresponding elastic spacer elements, which interconnect theclamping segments. These elastomeric spacer elements can be positivelyheld in the clamping segments and for this purpose the latter havecorresponding undercuts.

[0004] Such elastomeric spacer elements in association with colletchucks are e.g. known from U.S. Pat. No. 4,858,938. The elastomericmaterial spacer elements are inserted loose in corresponding undercutsand recesses of the clamping segments. Due to the fact that the elasticspacer elements do not have a significant connecting or joining force,in the unassembled state of the clamping chuck there is a danger thate.g. during transportation thereof the cohesion between the clampingsegments is lost. Such a loose connection is desirable because for wearreasons an easy replacement of the spacer elements is to be madepossible. However, due to the loose cohesion and loss of cohesionbetween the clamping segments during transportation, the collet chuckhas to be reassembled prior to each use, which involves unnecessarilyhigh setting-up costs. In the case of large, heavy chucks, an injuryrisk for the operator can arise due to the not always adequate cohesiondue to the loss of the connection between the clamping segments.

[0005] Problem and Solution

[0006] Therefore the problem of the invention is to provide a spacerelement and a collet chuck with a connection between the clampingsegments of a collet chuck, the connection being on the one hand easilyreleasable for detaching the spacer elements between the connectingpieces and on the other the collet chuck can be easily assembled andalso in the unclamped state thereof offers a reliable hold.

[0007] This problem is solved by a spacer element with a collet chuckhaving the features of claim 1 and a collet chuck having the features ofclaim 9. Preferred and advantageous developments of the invention formthe subject matter of further claims and are explained in greater detailhereinafter. By express reference the wording of the claims is made intopart of the content of the description.

[0008] For the positive connection of two adjacent clamping segments ofa collet chuck on two facing sides of a connecting segment, a spacerelement according to the invention has shaped sections. The spacerelement is made from flexible or elastomeric material. The shapedsections have in each case at least one opening or recess for theintroduction of in each case one widening component or element, e.g. anexpanding mandrel. As a result the shaped section can be widened orexpanded.

[0009] According to a further extending development sliding faces areprovided on the recesses. The sliding faces are in particular formed inthe contact area between the expanding mandrel and the recess. Thesliding faces are preferably made from non-elastomeric material and arein particular metallic. The sliding faces can be fixed in the vicinityof the recesses to the spacer elements in a non-detachable manner, e.g.by bonding or vulcanizing or injection moulding on.

[0010] In a preferred development of the invention the sliding faces areconstructed in the form of a cohesive and advantageously one-pieceintermediate piece. The intermediate piece can be constructed as across-sectionally round or elliptical and in particular circular tube.The tube can extend axially over the total length of the recess.

[0011] The intermediate piece advantageously has a slot extending overthe axial length. The slot particularly runs linearly and axially overthe total length of the intermediate piece. Alternatively the slot canbe spirally coiled. The spiral coil can advantageously be constructed insuch a way that over and beyond the axial length there is precisely oneturn of the axial coil. This measure ensures that the intermediate piececan be readily expanded and deformed. In addition, over the total lengthof the recess considered at any point of the circumference, at leastover a partial path, a supporting of the spacer element on theintermediate piece is ensured. This reliably avoids contact between thespacer element and the expanding mandrel when the latter is in theinoperative position.

[0012] According to a preferred embodiment of a spacer element, thelatter is cross-sectionally bone-shaped. It has two thickened, roundedend regions, which form shaped sections. It also has a web formedbetween the shaped sections and constituting the connecting piecebetween them. Preferably each of the thickened end regions has acentrally positioned, preferably round or elliptical, particularlyelongated hole-shaped or circular bore axially traversing the endregion. There is preferably a tubular, axially supported intermediatepiece on the insides of the bore.

[0013] A collet chuck according to the invention is particularly usedfor chucking workpieces. Such a collet chuck has at least two clampingsegments. Adjacent clamping segments are interconnected by elasticspacer elements, which can be constructed in the manner describedhereinbefore.

[0014] The clamping segments have undercuts, whilst the spacer elementshave correspondingly shaped shaped sections, so that a positiveengagement of the shaped sections of the spacer elements in theundercuts of the clamping segments is possible. According to theinvention an expanding mandrel is provided, which can be inserted in thevicinity of the undercuts and which ensures a frictional connectionbetween the clamping segment and spacer element. Thus, according to theinvention, there is no longer only a positive, but also a frictionalconnection between the clamping segment and the spacer element. Thefrictional connection is limited to the area of the undercuts in theclamping segment.

[0015] Due to the fact that the frictional connection takes place by theintroduction of the expanding mandrel in the vicinity of the undercuts,in addition to the positive connection between the spacer element andthe clamping segment a frictional connection is obtained. Thisconnection can be released in that the frictional connection is removedas soon as the expanding mandrel is taken away. In this case there isonce again only a positive connection between the spacer element and theclamping segment. In this state the closer, which comprises spacerelements and clamping segments, can be easily assembled anddisassembled. It is possible to individually replace without significanteffort and expenditure fatigued or damaged spacer elements. Only as aresult of the insertion of the expanding mandrels at the intendedlocations is the frictional connection produced, so that then a reliableand safe assembly state of the collet chuck is obtained.

[0016] According to an advantageous development of the invention asliding face is provided between the expanding mandrel and the spacerelement. The sliding face can be in the form of a one-piece intermediatepiece. The sliding faces of the intermediate piece, along which theexpanding mandrel moves during the insertion into the receptacleprovided, are made from a non-elastomeric material. The function of theintermediate piece or the sliding faces formed on the spacer element isto ensure that the expanding mandrel can be introduced into thecorresponding position without significant frictional resistance andwithout deformation or distortion of the spacer element. The slidingface or intermediate piece are in particular made from a metallicmaterial, which has a low frictional resistance with respect to theexpanding mandrel. An easily deformable metal, e.g. aluminium can beused. This has the advantage that such an intermediate piece is lightand can also be easily deformed. This may e.g. be necessary in order toproduce the frictional connection between spacer element and clampingsegment.

[0017] According to a further extending development of the invention theexpanding mandrel is held between the clamping segment and the spacerelement in the vicinity of the undercut and produces a frictionalconnection between the clamping segment and spacer element.Alternatively the spacer element can have a recess into which theexpanding mandrel can be introduced. Within the recess the expandingmandrel is completely surrounded by the spacer element. The recess inthe spacer element is preferably formed in the area in which theexpanding mandrel engages in the undercut of the clamping segment.According to a further extending development of the invention thefrictional connection between the spacer element and the clampingsegment can be brought about by elastic deformation of the recess. Sucha construction can in particular be advantageous if the spacer elementis bone-shaped. The rounded ends of the bone shape then engage in theundercuts of a clamping segment and between the rounded points there isa substantially rectangular connecting section. Each of the rounded eachsections can have a recess.

[0018] The recess can be round and in particular oval, e.g. beingpreferably in the form of an elongated hole. Preferably the longer majoraxis of the rounding or oval passes in the direction of the connectingsegment between the two round ends. Advantageously within the interiorof the recess is placed a spacer element, which is made from acorrespondingly shaped metal body having a through, axial slot. Into theinterior of this metal body can be introduced the expanding mandrel,which has the shape of the recess. By rotating the expanding mandrelafter the end of the introduction by an angle of 90ø, the rounded end ofthe bone-shaped end of the spacer element is deformed in such a way thatthere is a frictional connection between the spacer element and theclamping segment. The clamping segment has a recess corresponding to theouter contour of the bone-shaped spacer element and which isconsequently approximately circular in cross-section and into which thespacer element can be introduced. The rotation of the expanding mandrelreduces the diameter of the elastomeric part of the spacer elementbetween the recess and the clamping segment in the region of thegreatest mandrel width. The frictional connection is produced in thissection. The positive and frictional connection can in particular beensured if the undercut of the clamping segment serving to receive therounded end of the bone-shaped clamping segment has an outwardlydirected opening, whose width is smaller than the longest axis of theexpanding mandrel, i.e. the longest extension of the elongatedhole-shaped recess.

[0019] Preferably, according to the invention, a spacer element is ineach case placed between two adjacent clamping segments and the spacerelement is positively and non-positively held in each of the twoclamping segments.

[0020] In a particularly advantageous manner a collet chuck has a spacerelement as described hereinbefore and which can have one or more of theaforementioned features.

[0021] These and further features can be gathered from the claims,description and drawings and the individual features, both singly and inthe form of subcombinations, can be implemented in an embodiment of theinvention and in other fields and can represent advantageous,independently protectable constructions for which protection is claimedhere.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the invention are described in greater detailhereinafter relative to the attached drawings, wherein show:

[0023]FIG. 1 A cross-sectional, diagrammatic representation of aninventive positive and frictional connection between the two clampingsegments of a collet chuck by means of a bone-shaped spacer element.

[0024]FIG. 2 A diagrammatic ghosted view of the positive and frictionalconnection between a clamping segment and a spacer element by means ofan expanding mandrel insertable in a recess according to a firstembodiment.

[0025]FIG. 3 A second embodiment of a positive and frictional connectionbetween clamping segment and spacer element.

[0026]FIGS. 4 & 5 A third embodiment of a positive and frictionalconnection between clamping segment and spacer element in the releasedintermediate position and fixing end position.

[0027]FIG. 6 A front view of a collet chuck with several clampingsegments, adjacent clamping segments being in each case interconnectedvia a spacer element.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028]FIG. 1 shows in plan view two gripping or clamping segments 21 ofa collet chuck 20. Each of these clamping segments has an undercut 22.The undercut can be either axial or radial to the major axis of a colletchuck 20. The embodiment shown in this drawing and the other drawingsare essentially independent of whether the clamping segments 21 with thespacer elements 30 are aligned axially or radially relative to the majoraxis of the collet chuck 20. In the embodiment shown the undercut 22 isin the form of a cylindrical recess extending along its cylinder axis,which is in plan view perpendicular to the drawing plane. As stated, itis unimportant whether the extension axis of the undercut is axial, i.e.parallel to the major axis of the collet chuck 20, or radial thereto.

[0029] The spacer element 30 is positioned between the two clampingsegments 21. The spacer element 30 comprises two thickened end regionsand a connecting piece 32 linking said regions. The outer contour of thethickened end regions 31 is shaped in such a way that it can be insertedin the undercut 22 of the clamping segments 21 and at least partlypositively engages thereon. Each of the undercuts 22 of the clampingsegments 21 has an opening 23 towards the outside of said segment 21. Inthe vicinity of said opening 23 extends the connecting piece 32 of thespacer element 30 and which interconnects the finished end regions 31.Thus, overall the spacer element 30 is bone-shaped. In plan view theconnecting piece 32 is substantially parallelepipedic. The elasticity ofthe material of the connecting piece 32 essentially determines theelasticity and forces between the clamping segments 21 and thereforealso the damping characteristics of the collet chuck 20. By means of thematerial thickness and toughness of the material, especially of thespacer element 30, particularly in the vicinity of the connecting piece32, but also in the transition area between the thickened end regions 31and the connecting piece 32, the durability and toughness of the spacerelement are determined. The spacer element is a wearing part which hasto be regularly replaced.

[0030] In the thickened end region 31 and in particular centrallytherein, the spacer element 30 has an axially directed bore 33 forreceiving an expanding mandrel 40. The outer contour of the expandingmandrel 40 corresponds to the inner contour of the bore 33. However, thediameter of the expanding mandrel 40 has a certain oversize comparedwith the internal diameter of the bore 33 of the spacer element 30. Theamount of said oversize is determined as a function of the materialcharacteristics of the spacer element 30 and the deforming forces to beapplied, as well as the forces to be applied for producing thefrictional connection. The arrows 41 indicate that the forces arising asa result of the different diameter and which act from the expandingmandrel on the spacer element apply a holding force throughout the areawhere the spacer element engages positively on the undercut 22. Thus,following the insertion of the expanding mandrel a mechanically reliableholding of the material is ensured.

[0031] Substantially corresponding to FIG. 1, FIG. 2 is a perspectiveview of a clamping segment 22 cooperating with a spacer element.

[0032] The clamping segment 21 has an undercut 22 into which isintroduced the spacer element 30. The spacer element 30 is centrallyprovided in the thickened end region 31 positively engaging on theundercut 22 with a bore 33, which axially traverses the spacer element30. The axis of the bore 33 is oriented substantially parallel to thecentre axis of the undercut and passes centrally in the said undercut22. An intermediate piece 34 is placed in the spacer element 30 in thevicinity of the hole. The intermediate piece 34 extends axially over theentire length of the spacer element 30. Also radially the intermediatepiece 34 is interrupted by an axially directed, narrow slot 35. Thisslot 35 can be constructed in such a way that it passes through theentire axial length of the intermediate piece. However, it is alsopossible to have a different slot configuration, e.g. an axially coiled,spiral path, as well as a serrated slot shape, in which the teeth orserrations alternately project from both sides over the centre. Thus, inaxial view, over the entire circumferential distance at at least onepoint or at least over part of the axial length of the spacer element isprovided a portion of the intermediate piece. The intermediate pieceserves as a sliding element or bearing between the expanding mandrel 40and spacer element 30 in order to reduce the friction, which would bevery high particularly with elastomeric material or rubber. Theintermediate piece is firmly connected to the remaining spacer element30, e.g. by vulcanization or bonding. The intermediate piece ispreferably made from a metallic material, e.g. thin aluminium.

[0033] The expanding mandrel 40 has an external diameter larger than theinitial internal diameter of the spacer element 30, i.e. the internaldiameter of the tubular intermediate piece 34. In order to ensure goodinsertability of the expanding mandrel 40, it can be constructed in sucha way that it conically widens. The front end of the expanding mandrel40, which would be introduced first into the interior of the bore 33,would consequently have a smaller external diameter than the internaldiameter of the bore 33 in the outer region facing the expanding mandrel40.

[0034] In order to still ensure an engagement of the expanding mandrel40 over the entire length of the bore 33, it is possible for the bore toconically taper over its axial length. To still ensure a uniform seatingof the spacer element over the entire axial extension in the clampingsegment 21 and so as not to change the spring tensions through athickening spacer element material layer, it is also possible for boththe bore 33 and the spacer element 30 to conically taper. In order toachieve a corresponding positive engagement of the spacer element 30 inthe vicinity of the undercut 22 of the clamping segment 21, saidundercut 22 need not be cylindrical, but can also taper, e.g. conicallyover the axial length. However, in the inserted end position of theexpanding mandrel 40 the external diameter thereof at all points exceedsthe original internal width of the bore 33 and consequently theintermediate piece 34 at this point.

[0035] Through the introduction of the expanding mandrel into the spacerelement the positive connection between the spacer element and theclamping segment 21 is supplemented by an additional frictionalconnection.

[0036]FIG. 3 shows another embodiment of a positive and non-positiveconnection between a spacer element 30 and a clamping segment 21. Theclamping segment 21 has a groove-like undercut 22, at least one of thesides of the groove being bevelled in such a way that in the base of thegroove there is a greater width than on the upper groove edge. Thespacer element 30 comprises a connecting section 32, which extends atleast approximately to the upper groove edge and which is formed by theouter contour 24 of the clamping segment 21. The connecting piece 32 isparallelepipedic. The spacer element 30 then has a shaped section 36,which is parallel to the groove side slope and therefore engagespositively on the sloping groove area. On the inside of the shapedsection 36 remote from the slope is undetachably fixed a sliding face34, e.g. made from a metallic material. In the vicinity of said slidingface 34, the spacer element 30 has a recess 38, so that the spacerelement 30 at least fails to fill part of the groove area and into therecess 38 can be introduced an expanding mandrel 40. In the embodimentshown the expanding mandrel 40 engages along two sides, namely along theunbevelled groove sides, on the clamping segment 21. As a result of itscorrespondingly large external diameter over the sliding face 34, itpresses the material of the shaped section 36 against the bevelled sideof the groove. Thus, here there is not only a positive, but also africtional connection between the spacer element 30 and the clampingsegment 21. According to alternative developments it would be possiblefor the recess 38 to only be substantially triangular and to have on theunbevelled groove side part of the shaped section 36 of the elastomericmaterial of the spacer element 30, which can also have a sliding face onits inside. Thus, the expanding mandrel 40 engages on two sides on thespacer element 30 and on the clamping segment 21 only towards the groovebase.

[0037]FIG. 4 shows another embodiment of an inventive positive andnon-positive connection. FIG. 4 shows the situation where there is onlya positive connection between the spacer element 30 and the clampingsegment 21. FIG. 5 also shows the frictional connection.

[0038]FIG. 4 shows a spacer element 30 with a thickened end region 31and an intermediate piece 32, which is only shown in part sectional formand at whose other end is again connected a thickened end region 31. Theclamping segment 21 has an undercut 22, which is substantially oval. Theundercut can also be elongated hole-shaped. However, the oval,substantially elliptical shape with its two spaced focal pointsrepresents an appropriate construction. The connecting line between thetwo focal points preferably defines a first centre symmetry plane, whichis also continued in the vicinity of the connecting piece 32. A secondaxis of symmetry perpendicular thereto between the two focal points ofthe elliptical shape also defines a mirror symmetry axis with respect tothe shape of the thickened end region.

[0039] An elongated hole-shaped bore 33 is formed in each thickened endregion 31 of the spacer element 30. The elongated hole-shaped bore has alength which is smaller than the shorter major axis of the ellipticalundercut 22. The centre of the elongated hole-shaped bore is preferablycentral with respect to the undercut 22 and with respect to the centreof the thickened end region 31. An expanding mandrel 40, e.g. accordingto FIG. 2, can be inserted in the bore 33. However, it must be borne inmind that there must be a specific orientation of the expanding mandrel,which has an elongated hole-shape in accordance with the elongatedhole-shaped construction of the bore 33. For graphic simplificationpurposes the expanding mandrel 40 is not shown in FIGS. 4 and 5.

[0040] In accordance with the description regarding FIG. 2 it is alsopossible to have a conical taper of the elongated hole over the entireaxial extension thereof. Once again in accordance with the descriptionof FIG. 2, the greatest width of the cone is on the upper outside and inthe case of a radial arrangement of the spacer element, on the radiallyouter point and with an axial alignment of the spacer element on thefront of the collet chuck.

[0041] By

[0042] By rotating the expanding mandrel 40 introduced into the bore 33of the spacer element 30, there is now a passage from the situation inthe left-hand half to that in the right-hand half of the drawing.Through elastic deformation of the material of the spacer element 30,the alignment of the elongated hole is initially forcibly changed. Asthe spacing between the edge of the undercut 22 and the start of theexpanding mandrel 40, considered in the width direction, reduces in thethickening area, as a result of this elastic deformation and the changeto the alignment of the elongated hole, a frictional connection isproduced between the spacer element 30 and undercut 22. The situation ispreferably such that the elongated hole 33 is longer than the width ofthe opening 23 of the undercut 22. Thus, only if the spacer elementmaterial is torn, can the spacer element 30 be removed from theundercut. However, here there is also a clamping holding of the materialbetween the expanding mandrel 40 and the edge of the undercut. Thus,this process can only take place on releasing the frictional connection.

[0043] In a diagrammatic plan view FIG. 6 shows a collet chuck 20constituted by in all eight clamping segments 21, a spacer element 30being placed between every two clamping segments. Thus, there are in alleight spacer elements 30. According to the drawing use is made of spacerelements of the type shown in FIGS. 4 and 5. However, it is possible touse any other spacer element form or shape, particularly one of thosedescribed hereinbefore.

1. Spacer element for the positive connection of two adjacent clampingsegments (21) of a collet chuck (20), with shaped sections (36) formedon facing sides of a connecting segment (32), the spacer element (30)being made from elastomeric material, characterized in that the shapedsections (36) in each case have at least one recess for the introductionof in each case one widening element (40), particularly an expandingmandrel.
 2. Spacer element according to claim 1, characterized in thatsliding faces (34) are provided at the recesses.
 3. Spacer elementaccording to claim 2, characterized in that the sliding faces (34) areprovided in the contact area to the expanding mandrel (40).
 4. Spacerelement according to claim 2 or 3, characterized in that the slidingfaces (34) are made from non-elastomeric, preferably metallic material.5. Spacer element according to one of the claims 2 to 4, characterizedin that the sliding faces (34) are non-detachably fixed and inparticular bonded or vulcanized to the spacer elements (30) in thevicinity of the recesses.
 6. Spacer element according to one of theclaims 2 to 5, characterized in that the sliding faces are constructedas a cohesive, one-piece intermediate piece (34).
 7. Spacer elementaccording to claim 6, characterized in that the intermediate piece (34)is constructed as a cross-sectionally elliptical, particularly circulartube, which has a slot (35) extending in the axial direction andpreferably the slot is spirally coiled over the tube length.
 8. Spacerelement according to one of the preceding claims, characterized in thatthe spacer element (30) is cross-sectionally bone-shaped, the thickenedend regions (31) forming the shaped sections (36), the web between theshaped sections (36) forming the connecting piece (32), each thickenedend region (31) having a centrally positioned bore, which is elliptical,particularly elongated hole-shaped or circular and which axiallytraverses the end region and on the inside thereof is located a tubular,axially slotted intermediate piece (34).
 9. Collet chuck, particularlyfor chucking workpieces, with at least two clamping segments (20), inwhich: adjacent clamping segments are interconnected by elastic spacerelements (30), undercuts (22) are formed on the clamping segments, thespacer elements (30) have shaped sections for positive engagement in theundercuts of the clamping segments, characterized in that a wideningelement is provided and is insertable in the vicinity of the undercuts(22) and the widening element produces a frictional connection betweenat least one clamping segment (20) and at least one spacer element (30).10. Collet chuck according to claim 9, characterized in that thewidening element is constructed as an expanding mandrel (40) and betweenthe expanding mandrel and spacer element (40) are provided sliding faces(34), particularly in the form of a one-piece intermediate piece (34)and preferably the sliding faces (34) are made from non-elastomericmaterial.
 11. Collet chuck according to claim 9 or 10, characterized inthat the expanding mandrel (40) is held in the vicinity of the undercut(22) between the clamping segment (21) and spacer element (30) andproduces the frictional connection between clamping segment (21) andspacer element (30).
 12. Collet chuck according to one of the claims 9to 11, characterized in that the spacer element (30) has a recess, intowhich the expanding mandrel (40) can be introduced and in the recess iscompletely embraced by the spacer element (30).
 13. Collet chuckaccording to claim 12, characterized in that the frictional connectionby means of the expanding mandrel (40) is produced by elasticdeformation.
 14. Collet chuck according to one of the claims 9 to 13,characterized in that in each case between two adjacent clampingsegments (21) is provided a spacer element (30), which is positivelyheld in each of the two clamping segments (21).
 15. Collet chuckaccording to one of the claims 9 to 14, characterized in that it has aspacer element according to one of the claims 1 to 8.